libs/kaptan-spi: add nonblocking transfer contract

libs/kaptan-spi/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "kaptan-spi"
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+version.workspace = true
+
+[lints]
+workspace = true